1. FIELD OF THE INVENTION
This invention relates to an apparatus and method for making a paper web from stock. More specifically, this invention relates to a twin-wire former followed by a conventional press followed by an extended nip press.
2. INFORMATION DISCLOSURE STATEMENT
Typically, the forming and pressing sections of a papermaking machine are considered as separate sections and it is necessary to provide a pickup roll adjacent to the couch roll for transferring the formed web from the forming section to the press section.
U.S. Patent No. 3,906,853 to Wohlfarter, issued Sept. 23, 1975, teaches a twin-wire arrangement for removing water from fibrous material including cooperating press rolls 3 and 4 disposed respectively within the loops of the upper and lower wires as shown in FIG. 1 and as described at column 2, lines 53 to 62. However, as shown in FIG. 1 by the arrow attached to roll 4, the roll 4 moves in a vertical direction and therefore generates a squeezing action rather than a high pressure pressing nip required for current paper and board production.
Normally, the formed web passing between the pickup roll and the forming wire does not have a great deal of inherent strength and it has been found that difficulties have been experienced in transferring the newly-formed web from the forming section to the pressure section.
Furthermore, the the ever-increasing demand to decrease the length of the forming and press sections, a need exists to reduce the overall distance between the headbox and the emerging pressed web.
The present invention overcomes both of the aforementioned problems associated with the art of papermaking by having the lower forming wire extend directly through the first press nip.
Therefore, the primary objective of the present invention is to overcome the aforementioned inadequacies of the prior art apparatus and to provide an apparatus which makes a considerable and significant contribution to the papermaking art.
Another object of the present invention is the provision of an apparatus for making a paper web in which the second wire extends through a first press nip.
Another object of the present invention is the provision of a twin-wire former in which a headbox is disposed adjacent to a first end of a forming section defined by a first and a second wire with the second wire supporting the formed web through a first press nip.
Another object of the present invention is the provision of an apparatus for making a paper web in which the second wire extends through a first nip defined by an open roll and a cooperating suction roll.
Another object of the present invention is the provision of an apparatus for making a paper web in which the open roll is looped by a first felt with the first felt running contiguously with the second wire before extending through the first press nip.
Another object of the present invention is the provision of an apparatus for making a paper web in which the pressed web is transferred to and thereafter supported by a second felt which loops the suction roll, the second felt guiding the web through a downstream extended nip press.
Another object of the present invention is the provision of an apparatus for making a paper web in which the web is heated by steam downstream relative to the first press nip and before passage of the pressed web through the extended nip.
Other objects and advantages of the present invention will be apparent to those skilled in the art by a consideration of the detailed description contained hereinafter taken in conjunction with the annexed drawings.